Method and apparatus for manufacturing plate-like structure

ABSTRACT

A method for manufacturing a plate-like structure, the method including a step of transferring concave and convex patterns on a master to a surface of a transferred substrate by sandwiching the master provided with the concave and convex patterns and the transferred substrate, between a press surface of a hollow cylindrical upper and a press surface of a lower mold, and pressurizing central parts of the upper and lower molds to apply pressure to the master and the transferred substrate, wherein a compressive load imposed on inner peripheral portions of the upper and lower molds is blocked and distributed toward outer peripheries of the upper and lower molds.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Applications No. 2004-278674, filed Sep. 27, 2004;and No. 2004-355792, filed Dec. 8, 2004, the entire contents of both ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus formanufacturing a plate-like structure, for example, recording media suchas a hard disk, a semiconductor, or a magnetic transfer disk.

2. Description of the Related Art

In recent years, significant enhancement of information equipment suchas personal computers has sharply increased the amount of informationthat must be handled by users. In this situation, expectations are beingplaced on information recording and reproducing apparatuses having amuch higher recording density or semiconductor devices having a muchhigher degree of integration.

A finer machining technique is required to improve the recording densityof recording media. Conventional photolithography techniques using anexposure process enable a large area to be micromachined at one time.However, these techniques do not provide a resolution equal to or lessthan the wavelength of light. Thus, it is difficult to form amicrostructure of a size of at most 200 nm using the conventionalphotolithography technique.

Examples of machining techniques for a size of at most 200 nm includeelectron beam lithography and focused ion beam lithography. However,disadvantageously, these techniques cannot provide a high throughput.

A “nano imprint lithography (NIL) technique” proposed by S. Y. Chou in1995 is used to form microstructures of size equal to or smaller thanthe wavelength of light (see, for example, Appl. Phys. Lett.; Vol. 76(1995) P3114).

The nano imprint lithography technique involves pressing a master onwhich fine concave and convex patterns have been formed using theelectron beam lithography or the like, against a substrate coated with aresist, to transfer the concave and convex patterns on the master to theresist film.

This technique sharply reduces the time required to process an area ofat least 1 square inch compared to the electron beam lithography orfocused ion beam lithography.

The steps of nano imprint lithography are as follows.

(1) A resist such as PMMA is applied to a transferred substrate such asa silicon substrate.

(2) The master is pressed against the transferred substrate in a reducedpressure atmosphere. In this case, the pressure is about 100 atm.

(3) The transferred substrate provided with the resist film is heated toat least the glass transition temperature of the resist.

(4) A predetermined time later, the master and the transferred substrateare cooled to room temperature.

(5) The master is stripped off from the transferred substrate.

(6) Concaves and convexes are transferred to the resist film.

Of these steps, the step (3) of heating the transferred substrate to theglass transition temperature of the resist is required to soften theresist to enable the concaves and convexes to be transferred even undera low pressure. However, it takes a long time to heat and cool thetransferred substrate, thus lowering throughput. Moreover, the softenedresist causes the resist film to attach partly to the master and thus bestripped off from the substrate.

Further, these steps are executed in a reduced pressure atmosphere. Thisis to prevent transfers from being locally disabled owing to thepresence of bubbles between the master and the transferred substrate.However, in forming a reduced pressure atmosphere, a long time isrequired for deaeration using a pump or the like. This also reduces thethroughput.

Further, if the concave and convex patterns on the master are uniformlytransferred to a large area of about at least 1 square inch, a highparallelism is required between the surface of the master and thesurface of the transferred substrate. Even if the required parallelismis obtained, it is very difficult to uniformly distribute a load overthe large area.

As described above, the nano imprint lithography technique is suitablefor forming a microstructure of a size equal to or smaller than thewavelength of light. The nano imprint lithography enables amicrostructure to be formed with a much higher throughput than a drawingprocess using the electron beam lithography or focused ion beamlithography.

However, problems with the nano imprint lithography technique are thatthe throughput is affected by the time required to heat and cool thesubstrate, that the film may be stripped, that the time required fordeaeration affects the throughput, and that it is difficult to ensurethe parallelism between the surface of the master and the surface of thetransferred substrate and to apply a uniform load to the master andtransferred substrate.

In order to solve these problems, the applicant has proposed a roomtemperature imprint technology (see, for example, Jpn. Pat. Appln. KOKAIPublication No. 2003-157520).

With the room temperature imprint technology, a master and a transferredsubstrate are sandwiched between a pair of press surfaces under roomtemperature; the master has a concave and convex region provided withconcave and convex patterns and the transferred substrate is coated witha resist. A very high pressure is then applied to the master andtransferred substrate to transfer the concave and convex patterns on themaster to the resist film on the transferred substrate.

This technique allows the concave and convex formed region of the masterexcept for blank parts to be pressed against the transferred substrateunder a uniform pressure. Consequently, fine concave and convex patternsof size 200 nm or less are uniformly transferred to the transferredsubstrate over a large area. A high throughput is also achieved.

Further, even under atmospheric pressure, when a pressure of at least500 atm. is applied to the master and transferred substrate, compressedbubbles serve as a protective layer. Accordingly, the master and thetransferred substrate are reliably and easily separated from each otherto avoid problems such as tear-off of the film.

As described above, the room temperature imprint technique eliminatesthe disadvantages of the “nano imprint lithography (NIL) technique”proposed by S. Y. Chou. However, the room temperature imprint techniquepresents the problems described below.

A first problem is that under a pressure of at least 500 atm., elasticdeformation of a mold causes a biased abutment phenomenon. Thisprecludes the master and the transferred substrate from being subjectedto a uniform pressure.

FIG. 23 is a partly cutaway perspective view of a press machine used fora press process with the room temperature imprint technique.

In FIG. 23, reference numerals 101, 102, and 103 denote a master, atransferred substrate, and an upper mold, respectively. Referencenumerals 104 and 105 denote an upper base and a lower mold,respectively. Reference numeral 106 denotes a lower base.

The upper base 104 has a disk-like larger-diameter portion 104 a and adisk-like smaller-diameter portion 104 b formed on a bottom surface ofthe larger-diameter portion 104 a concentrically with thelarger-diameter portion 104 a. The upper mold 103 is shaped like a donutand is embedded in a central part of the smaller-diameter portion 104 b.

The lower base 106 is composed of a disk-like larger-diameter portion106 a and a disk-like smaller-diameter portion 106 b formed on a topsurface of the larger-diameter portion 106 a concentrically with thelarger-diameter portion 106 a. A cylindrical projection 106 c is formedso as to extend upward through central holes in the master 101 andtransferred substrate 102. The outer diameter of the projection 106 c isslightly smaller than the inner diameter of a central hole in the uppermold 10. The lower mold 105 is shaped like a donut and embedded aroundthe periphery of the projection 106 c.

FIG. 24 is a graph showing the distribution of pressure generated whenthe master and the transferred substrate were pressurized at 1,000 atm.using the press machine used for the press process with the roomtemperature imprint technique.

FIG. 24 shows that there is a difference of about 20% in pressure. Thisindicates that the master and the transferred substrate are notsubjected to a uniform pressure.

A second problem is the relative misalignment between the master and thetransferred substrate.

FIG. 25A is a sectional view showing the master and transferredsubstrate before the press process with the room temperature imprinttechnique. FIG. 25B is a sectional view showing the master andtransferred substrate during the press process with the room temperatureimprint technique.

As previously described, with the room temperature imprint technique,the master and the transferred substrate are subjected to a highpressure of at least 500 atm. Thus, the master and the transferredsubstrate contract significantly in a vertical direction (in which thepressure is applied) and expand markedly in a horizontal direction(which is perpendicular to the vertical direction).

A Poisson ratio is the ratio of the amount by which the master andtransferred substrate contract in the vertical direction to the amountby which the master and transferred substrate expand in the horizontaldirection. Every substance has its specific Poisson ratio. The amount bywhich the master and the transferred substrate expand in the horizontaldirection is in proportion to compressive stress and the Poisson ratioand in inverse proportion to the modulus of longitudinal elasticity.

For example, nickel has a modulus of longitudinal elasticity of1.995×10¹¹ Pa and a Poisson ratio of 0.31. Glass has a modulus oflongitudinal elasticity of 7.200×10¹⁰ Pa and a Poisson ratio of 0.30.

Accordingly, if the material for the master 101 is nickel and thematerial for the transferred substrate 102 is glass, the master 101 andthe transferred substrate 102 have significantly different moduli oflongitudinal elasticity from each other. Consequently, misalignmentunavoidably occurs between the master 101 and the transferred substrate102.

Frictional force acts on the upper mold 103, the lower mold 105, themaster 101, and the transferred substrate 102. Thus, with a uniformpressure distribution, the frictional force surpasses a horizontallyexpanding force to prevent the misalignment between the master 101 andthe transferred substrate 102. However, as previously described, theroom temperature imprint technique entails a nonuniform pressuredistribution. This results in the misalignment between the master 101and the transferred substrate 102.

FIG. 26 is a graph showing the amount of relative misalignment betweenthe master and the transferred substrate observed if the roomtemperature imprint technique is used. In FIG. 26, a denotes the amountof misalignment attributed to the room temperature imprint technique,and b denotes a line corresponding to a misalignment amount of zero.

FIG. 26 shows that the amount of misalignment between the master and thetransferred substrate is about 20 nm. This misalignment amount isimpermissible if patterns of a size of at most 200 nm are to be formed.

It is an object of the present invention to solve problems (1) to (5)listed below and accompanying the nano imprint lithography technique aswell as problems (7) to (6) listed below and accompanying the roomtemperature imprint technique.

(1) A long time is required to heat and cool the substrate, thuslowering the throughput.

(2) When the master is stripped off from the transferred substrate, theresist film may be stripped off from the transferred substrate.

(3) A long time is required deaeration, thus lowering the throughput.

(4) It is difficult to ensure the parallelism between the surface of themaster and the surface of the transferred substrate and to apply auniform pressure to the master and transferred substrate.

(5) During heating or cooling, a difference in coefficient of thermalexpansion may result in the relative misalignment between the master andthe transferred substrate.

(6) A nonuniform pressure is exerted on the transferred substrate.

(7) A difference in material may lead to the relative misalignmentbetween the master and the transferred substrate.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, a method formanufacturing a plate-like structure is configured as described below.

The aspect of the present invention provides a method for manufacturinga plate-like structure, the method comprising a step of transferringconcave and convex patterns on a master to a surface of a transferredsubstrate by sandwiching the master provided with the concave and convexpatterns and the transferred substrate, between a press surface of ahollow cylindrical upper mold and a press surface of a hollowcylindrical lower mold, and pressurizing central parts of the upper andlower molds to apply pressure to the master and the transferredsubstrate, wherein a compressive load imposed on inner peripheralportions of the upper and lower molds is blocked and distributed towardouter peripheries of the upper and lower molds.

According to another aspect of the present invention, a method formanufacturing a plate-like structure is configured as described below.

The aspect of the present invention provides a method for manufacturinga plate-like structure, the method comprising a step of transferringconcave and convex patterns on a master to a surface of a transferredsubstrate by sandwiching the master provided with the concave and convexpatterns and the transferred substrate, between a press surface of anupper mold and a press surface of a lower mold, and applying pressure tothe master and the transferred substrate, wherein a compressive loadimposed on outer peripheral portions of the upper and lower molds isdistributed toward central axes of the upper and lower molds.

According to another aspect of the present invention, an apparatus whichmanufactures a plate-like structure is configured as described below.

The aspect of the present invention provides an apparatus whichmanufactures a plate-like structure, the apparatus transferring concaveand convex patterns on a master to a surface of a transferred substrateby sandwiching the master provided with the concave and convex patternsand the transferred substrate, between a press surface of a hollowcylindrical upper mold and a press surface of a hollow cylindrical lowermold, and applying pressure to the master and the transferred substrate,wherein the apparatus comprises grooves formed in inner peripheralsurfaces of the upper and lower molds to block a compressive loadconcentrating at inner peripheral portions of the upper and lower moldsto distribute the compressive load toward outer peripheries of the upperand lower molds.

According to another aspect of the present invention, an apparatus whichmanufactures a plate-like structure is configured as described below.

The aspect of the present invention provides an apparatus whichmanufactures a plate-like structure, the apparatus transferring concaveand convex patterns on a master to a surface of a transferred substrateby sandwiching the master provided with the concave and convex patternsand the transferred substrate, between a press surface of an upper moldand a press surface of a lower mold, and applying pressure to the masterand the transferred substrate, wherein the apparatus comprises groovesformed in outer peripheral surfaces of the upper and lower molds todistribute a compressive load concentrating at outer peripheral portionsof the upper and lower molds toward central axes of the upper and lowermolds.

The present invention enables the high-throughput and high-yieldmanufacturing of high-density recording media, semiconductors, andmagnetic recording media having fine concave and convex patterns.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1A is a process diagram of a process for manufacturing magneticrecording media according to a first embodiment of the presentinvention;

FIG. 1B is a process diagram of the process for manufacturing magneticrecording media according to the first embodiment;

FIG. 1C is a process diagram of the process for manufacturing magneticrecording media according to the first embodiment;

FIG. 1D is a process diagram of the process for manufacturing magneticrecording media according to the first embodiment;

FIG. 1E is a process diagram of the process for manufacturing magneticrecording media according to the first embodiment;

FIG. 1F is a process diagram of the process for manufacturing magneticrecording media according to the first embodiment;

FIG. 2 is a perspective view of a manufacturing apparatus according tothe first embodiment;

FIG. 3 is a perspective view of the manufacturing apparatus according tothe first embodiment as viewed from a direction different from that inFIG. 2;

FIG. 4 is an exploded perspective view of an essential part of themanufacturing apparatus according to the first embodiment;

FIG. 5 is an enlarged view of a free shank according to the firstembodiment;

FIG. 6 is a front view of a common hydraulic press machine used to pressthe manufacturing apparatus according to the first embodiment;

FIG. 7 is an exploded perspective view of a mold used to produce a2.5-inch hard disk according to the first embodiment;

FIG. 8 is a diagram illustrating a method for applying pressure to themold according to the first embodiment;

FIG. 9A is a diagram showing the distribution of stress acting on themanufacturing apparatus according to the first embodiment in a verticaldirection;

FIG. 9B is an enlarged view of an essential part of FIG. 9A;

FIG. 10 is a graph showing the distribution of pressure generatedbetween a master and a transferred substrate according to the firstembodiment;

FIG. 11 is a graph showing the amount of relative misalignment betweenthe master and the transferred substrate according to the firstembodiment;

FIG. 12A is a process diagram of a process for manufacturing phasechange optical recording media according to a second embodiment of thepresent invention;

FIG. 12B is a process diagram of the process for manufacturing phasechange optical recording media according to the second embodiment;

FIG. 12C is a process diagram of the process for manufacturing phasechange optical recording media according to the second embodiment;

FIG. 12D is a process diagram of the process for manufacturing phasechange optical recording media according to the second embodiment;

FIG. 12E is a process diagram of the process for manufacturing phasechange optical recording media according to the second embodiment;

FIG. 12F is a process diagram of the process for manufacturing phasechange optical recording media according to the second embodiment;

FIG. 13 is a sectional view of a manufacturing apparatus according to afourth embodiment of the present invention;

FIG. 14 is a sectional view showing an essential part of a transferredsubstrate 1 pressurized by an upper and lower molds according to a fifthembodiment of the present invention;

FIG. 15A is a graph showing the distribution of pressure generatedbetween a master and a transferred substrate according to the fifthembodiment;

FIG. 15B is a graph showing the amount of relative misalignment betweenthe master and the transferred substrate according to the fifthembodiment;

FIG. 16A is a perspective view of a manufacturing apparatus according tothe fifth embodiment;

FIG. 16B is a partly cutaway perspective view of the manufacturingapparatus according to the fifth embodiment;

FIG. 17 is an enlarged sectional view showing an essential part of FIG.16B;

FIG. 18 is a view illustrating a method for applying pressure to a moldaccording to the fifth embodiment;

FIG. 19A is a graph showing the distribution of pressure generatedbetween a master and a transferred substrate according to the fifthembodiment;

FIG. 19B is a graph showing the amount of relative misalignment betweenthe master and the transferred substrate according to the fifthembodiment;

FIG. 20A is a sectional view of a pressure equalizer in which nopressure is applied to the master and transferred substrate according tothe fifth embodiment;

FIG. 20B is a sectional view of a pressure equalizer in which pressureis applied to the master and transferred substrate according to thefifth embodiment;

FIG. 21A is a graph showing the distribution of pressure generatedbetween the master and the transferred substrate if a manufacturingapparatus according to a variation of the fifth embodiment is used;

FIG. 21B is a graph showing the amount of relative misalignment betweenthe master and the transferred substrate if a manufacturing apparatusaccording to a variation of the fifth embodiment is used;

FIG. 22 is a partly cutaway perspective view of a manufacturingapparatus according to a sixth embodiment of the present invention;

FIG. 23 is a partly cutaway perspective view of a press machine used fora press process with the room temperature imprint technique;

FIG. 24 is a graph showing the distribution of pressure generated whenthe master and the transferred substrate are pressurized under apressure of 1,000 atm using the press machine utilized for the pressprocess with the room temperature imprint technique;

FIG. 25A is a sectional view showing the master and the transferredsubstrate before the press process with the room temperature imprinttechnique;

FIG. 25B is a sectional view showing the master and the transferredsubstrate during the press process with the room temperature imprinttechnique; and

FIG. 26 is a graph showing the amount of relative misalignment betweenthe master and the transferred substrate if the room temperature imprinttechnique is used.

DETAILED DESCRIPTION OF THE INVENTION

A first to fifth embodiments of the present invention will be describedbelow in detail with reference to the drawings.

First Embodiment

In the first embodiment, a groove region is formed on a substrate usingnano imprinting according to the present invention. A magnetic materialis filled into the groove region to create a recording track band. Inthis case, a plate-like structure is assumed to be a magnetic diskcontained in a 2.5-inch hard disk.

FIGS. 1A to 1F are process diagrams of a process for manufacturingmagnetic recording media (plate-like structure) according to the firstembodiment of the present invention. FIGS. 1A to 1F are also schematicsectional views of a workpiece during the respective steps.

A transferred substrate 1 shown in FIG. 1A is produced. Specifically, asoft magnetic layer and a vertical-recording magnetic film are depositedon a glass disk substrate 2 by a sputtering method; the soft magneticlayer consists of a ruthenium alloy and the magnetic film comprises arecording layer consisting of a cobalt alloy. The glass disk substrate 2used is shaped like a hollow disk of a diameter of 65 mm having a hollowportion formed along a central axis. In the description below, a“magnetic film 3” indicates the soft magnetic layer and the magneticfilm. A novolack type resist film 4 is deposited on the magnetic film 3to a thickness of 100 nm by spin coating.

Then, as shown in FIG. 1B, a master 5 is pressed against the resist film4 to transfer concave and convex patterns on the master 5 to a surfaceof the resist film 4. As described later, the master 5 comprises aconcave and convex formed region 5 a provided with a plurality ofconcave and convex patterns. This process is nano imprinting.

Then, as shown in FIG. 1C, the master 5 is stripped off from thetransferred substrate 1. Thus, when nano imprinting is finished, theconcave and convex patterns corresponding to the concave and convexpatterns on the master 5 have been formed on the surface of the resistfilm 4 on the transferred substrate 1.

Then, as shown in FIG. 1D, the residues of the resist film 4 are removedby etching (RIE).

Then, as shown in FIG. 1E, an argon ion milling process is executed onthe resist film 4 and magnetic film 3 in the transferred substrate 1 toetch the magnetic film 3. On this occasion, the milling process removesthe magnetic film 3 from the part of the resist film 4 which correspondsto the groove. The milling process etches a part of the whole resistfilm 4 except for the groove. However, the etching does not reach themagnetic film 3. Consequently, the patterned magnetic substance 3 aremains.

As shown in FIG. 1F, an oxygen ashing process is executed on theworkpiece thus obtained to remove the residual resist. Thus, a recordingtrack band comprising a patterning magnetic substance 3 a is formed onthe glass disk substrate 2. Disk-like recording media D is completed.

A material for the transferred substrate 1 is desirably suitable forhigh-density recording media to be produced. For example, the substratematerial contains a metal, alloy, metal oxide, an inorganic material, aceramic material, a semiconductor, glass, or a compound or mixturecontaining at least two of these materials.

A material for the resist film 4 is desirably suitable for a processsuch as etching which is executed after the nano imprint processdepending on the high-density recording media to be produced. Thematerial is, for example, a common resist material or polymer materialused for a semiconductor process.

Moreover, the resist film 4 must have the concave and convex patterns onthe master 5 reliably transferred to itself by nano imprinting. Thus,the resist material is desirably softer than the material for the master5.

Further, the resist material is preferably stable so that the concaveand convex patters transferred at room temperature are maintained afterthe nano imprint process. That is, the resist material desirably has aglass transition temperature and a melting point which are both equal toor higher than the room temperature. Moreover, the resist material isdesirably soft enough to allow the concave and convex patterns on themaster 5 to be transferred to itself even with a load of at least 500atm.

The master 5 is produced as described below.

First, electron beam lithography is used to form a large number ofgroove structures with various shapes on a glass master. These groovestructures have a width of at most 200 nm, a spacing of at most 200 nm,and a height of at most 200 nm.

Then, a plating method is used to form a nickel film of a thickness 300μm on a surface of the glass master. Subsequently, the nickel film isstripped off from the glass master and cut. This forms concentricconcave and convex patterns having a width of at most 200 nm, a spacingof at most 200 nm, and a height of at most 200 nm. A nickel master 5 ofa diameter of 65 mm and a thickness of 300 μm is completed.

The material for the master 5 is desirably chosen such that the concaveand convex patterns formed on the surface of the master 5 are unlikelyto be deformed during nano imprinting. The material is, for example, ametal, an alloy, a metal oxide, an inorganic material, a ceramicmaterial, a semiconductor, glass, or a compound or mixture containing atleast two of these materials.

Further, the master 5 is desirably deformed to follow an accidentalswell in the surface of the transferred substrate 1. That is, the master5 is desirably formed of a material softer than that for the upper mold9 and lower mold 10. The inventor's examinations demonstrate that goodresults are obtained by using nickel (Ni), aluminum (Al), or the like asa material for the master 5. It has also been found that good resultsare obtained when the master 5 has a thickness of about 300 μm.

The concave and convex patterns formed in the concave and convex formedregion 5 a of the master 5 have a structure that is at most 200 nm insize so as to be suitably used for production of high-density recordingmedia. Examples of this structure include a groove structure of a widthof at most 200 nm, a ridge structure of a width of at most 200 nm, a dotstructure of a diameter of at most 200 nm, a columnar structure of adiameter of at most 200 nm, and a hole-like structure of a diameter ofat most 200 nm.

The depth of the concave and convex patterns is preferably at most 200nm, which is suitable for a semiconductor process such as etching whichis executed after the nano imprint process. Further, a groove part ofthe concave and convex patterns are desirably tapered at an angle of 1to 60° so as to be fanned toward the transferred substrate 1 so that thetransferred substrate 1 is easily stripped off from the master 5 afterthe nano imprint process. Moreover, the top and bottom of the concaveand convex patterns have a flat structure of roughness at most 10 nm soas to allow a magnetic substance to be accurately formed.

Now, description will be given of a nano imprinting method and amanufacturing apparatus.

FIG. 2 is a perspective view of a manufacturing apparatus according tothe first embodiment. FIG. 3 is a perspective view of the manufacturingapparatus according to the first embodiment as viewed from a directiondifferent from that in FIG. 2. FIG. 4 is an exploded perspective view ofan essential part of the manufacturing apparatus according to the firstembodiment.

As shown in FIGS. 2 to 4, the manufacturing apparatus comprises a freeshank 6, an upper die set 7, an upper plate 8, an upper mold 9, a lowermold 10, a lower plate 11, a lower die set 12, and a projection 13. Themanufacturing apparatus is pressurized from above by a hydraulic pressmachine. The position of the master 5 can be replaced with the positionof the transferred substrate 1.

The upper die set 7 is combined with the lower die set 12 via aplurality of guide posts 14 so that the upper die set 7 can freelycontact and leave the lower die set 12. The upper plate 8 is mounted ona bottom surface of the upper die set 7. The upper mold 9 is supportedon a bottom surface of the upper plate 8. The lower plate 11 is mountedon a top surface of the lower die set 12. The lower mold 10 is supportedon a top surface of the lower plate 11.

The projection 13 is provided on a top surface of a base 15 fixed to thehydraulic press machine to support a central part of bottom surface ofthe lower die set 12. A top surface of the projection 13 has a diametersmaller than that of the work piece (master 5 and transferred substrate1).

A pair of press surfaces according to the present invention is composedof a bottom surface of the upper mold 9 and a top surface of the lowermold 10. The master 5 and the transferred substrate 1 are sandwiched andpressurized between the press surfaces.

FIG. 5 is an enlarged view of the free shank 6 according to the firstembodiment.

As shown in FIG. 5, the free shank 6 is almost cylindrical and is mainlycomposed of an upper part, an intermediate part, and a lower part. Thetop surface of the upper part is spherical. A groove 6 b is formed inthe intermediate part all along the circumference of the free shank 6. Ashaft portion 6 a projects perpendicularly from a central part of bottomsurface of the lower part. The shaft portion 6 a is threaded in itsouter peripheral part. The shaft portion 6 a is screwed into a screwhole formed in the top surface of the upper die set 7. Thus, the freeshank 6 is fixed to the upper die set 7.

The bottom surface of the free shank 6 has a diameter smaller than thatof the workpiece; the top surface of the free shank 6 contacts the topsurface of the upper die set 7.

FIG. 6 is a front view of a common hydraulic press machine used to pressthe manufacturing apparatus according to the first embodiment.

In operation, the above manufacturing apparatus is mounted in a commonhydraulic press machine such as the one shown in FIG. 6. The hydraulicpress machine comprises a plurality of guide bars 16 provided on theleft and right of the position at which the manufacturing apparatus ismounted, a stage 17 moved up and down by guiding it along the guide bars16, and a holder 18 attached to a bottom surface of the stage 17.

The upper part of the free shank 6 is inserted into a hole 18 a formedin the holder 18. This allows the manufacturing apparatus to beinstalled on the holder 18. The free shank 6 is held by the holder 18 soas to be rotatable around a central axis.

When the central part of top surface of the free shank 6 is presseddownward by the holder 18, the projection 13 of the manufacturingapparatus receives this force. This causes the pressure to betransmitted to the workpiece sandwiched between the upper mold 9 and thelower mold 10.

Now, description will be given of pressure applied by the upper mold 9and lower mold 10 during nano imprinting.

In the present embodiment, nano imprinting is executed under atmosphericpressure. The pressure during nano imprinting is set to at least 500atm. This eliminates the need to increase the temperature during nanoimprinting to at least the glass transition temperature of the resistfilm 4. Consequently, the concave and convex patterns on the master 5are transferred to the transferred substrate even at room temperature oreven at 80° or lower even if heating is executed. This eliminates ordrastically reduces the time required to heat and cool the master 5 andthe transferred substrate 1. As a result, the throughput is greatlyimproved.

Moreover, when the pressure during nano imprinting is set to at least500 atm, bubbles remaining between the master 5 and the transferredsubstrate 1 are compressed so that their size is reduced to at most1/500. This substantially eliminates a mistake in the transfer of theconcave and convex patterns caused by the bubbles.

Further, when the master 5 is stripped off from the transferredsubstrate 1, the bubbles compressed during nano imprinting attempt toreturn to their original volume. The master 5 is thus pushed so as toseparate from the transferred substrate 1. This prevents the resist film4 from attaching to and remaining on the master 5. That is, the bubblescompressed under a high pressure are interposed between the master 5 andthe transferred substrate 1; the bubbles serve as a protective layerwhich is thin but which avoids impairing the concave and convexpatterns, to suppress tear-off of the resist film 4.

The press surfaces of the upper mold 9 and lower mold 10 are desirablyvery flat. Specifically, the press surfaces preferably have a surfaceroughness of less than 10 μm and more preferably less than 1 μm in thevicinity of the master 5 and transferred substrate 1, on which nanoimprinting is executed.

There is preferably a high parallelism between the press surfaces of theupper mold 9 and lower mold 10. Specifically, when the manufacturingapparatus is pushed without sandwiching the master 5 and the transferredsubstrate 1, the gap created between the press surfaces of the uppermold 9 and lower mold 10 is preferably less than 10 μm and morepreferably 1 μm. Provided that the press surfaces of the upper mold 9and lower mold 10 meet these conditions, problems can be prevented whichoriginate from the biased abutment between the upper mold 9 and thelower mold 10.

Possible materials for the upper mold 9 and lower mold 10 include lowcarbon steel, stainless steel, aluminum alloy, cemented carbide, or thelike, in view of their availability, cost, and the like.

Now, description will be given of a method for pushing the master 5against the transferred substrate 1 under a uniform pressure.

FIG. 7 is an exploded perspective view of a mold used to produce a2.5-inch hard disk according to the first embodiment.

As shown in FIG. 7, grooves 9 a and 10 a are formed in inner peripheralsurfaces of the upper mold 9 and lower mold 10 along a circumferentialdirection respectively.

FIG. 8 is a diagram illustrating a method for applying a pressure to themold according to the first embodiment.

As shown arrows in FIG. 8, pressure is applied so as to concentrate atthe central part between the upper mold 9 and the lower mold 10.

Now, description will be given of the characteristics of the structureof the mold according to the present embodiment.

Each of the upper mold 9 and lower mold 10 is formed like a cylinderhaving an outer diameter of 65 mm, an inner diameter of 20 mm, and athickness of 25 mm. A groove 10 a of a height of 1 mm and a depth of 1.8mm is formed in the inner peripheral surface of the lower mold 10 at aposition 2 mm away from the bottom surface of the lower mold 10. Agroove 9 a of a height of 1 mm and a depth of 1.8 mm is formed in theinner peripheral surface of the upper mold 9 at a position 2 mm awayfrom the top surface of the upper mold 9. Low-carbon steel or stainlesssteel is used as a material for the upper mold 9 and lower mold 10.

The hollow portions of the master 5, transferred substrate 1, upper mold9, and lower mold 10 are formed so as to determine their relativepositions. The pin 11 a of the lower plate 11 is inserted through thehollow portions. The hollow portions of the master 5, transferredsubstrate 1, upper mold 9, and lower mold 10 should have a diameter thatis the same as the outer diameter of the pin 11 a. However, the diameterof the pin 11 a is set slightly larger than that of the hollow portions(that is, by 5 to 20 μm) so as to allow the master 5, transferredsubstrate 1, upper mold 9, and lower mold 10 to be smoothly fittedaround and removed from the pin 11 a. This creates a gap between theinner peripheral surface of each of the master 5, transferred substrate1, upper mold 9, and lower mold 10 and the outer peripheral surface ofthe pin 11 a of the lower plate 11.

Further, the outer diameter of the upper mold 9 and lower mold 10 is setslightly smaller than that of the master 5 or transferred substrate 1.For example, if the gap is 10 μm in size, the outer diameter of theupper mold 9 and lower mold 10 is set smaller than that of the master 5or transferred-substrate 1 by 10 μm plus a margin to allow formanufacturing error in hole position. This prevents the localconcentration of stress.

The upper mold 9 and the lower mold 10 are attached to the hydraulicpress machine via the free shank 6. A pressure concentrating mechanism(pressure concentrating means) K allows the pressure exerted by thehydraulic press machine to concentrate at the corner of the upper mold 9and lower mold 10; the pressure concentrating mechanism consists of thefree shank 6 and the projection 13. The pressure concentrating mechanismK is shown in FIGS. 2 and 3.

Now, description will be given of the reason why the grooves 9 a and 10a are formed in the upper mold 9 and lower mold 10 respectively.

FIG. 9A is a diagram showing the distribution of stress acting on themanufacturing apparatus according to the first embodiment in thevertical direction. FIG. 9B is an enlarged view of an essential part ofFIG. 9A.

In this case, a pressure of 10⁸ Pa (about 1,000 atm.) is assumed.

As shown in FIG. 9A, a substantially uniform stress acts on the master 5and transferred substrate 1. This indicates that the master 5 and thetransferred substrate are subjected to the substantially uniformpressure.

The pressure concentrating mechanism K causes the pressure from thehydraulic press machine to concentrate at the center of the upper dieset 7 and lower die set 12; the pressure concentrating mechanism K iscomposed of the free shank 6 and the projection 13. Thus, in the uppermold 9, a compressive load concentrates at the inner peripheral part(see a part A), that is, the hollow portion H.

Accordingly, without the groove 9 a, the compressive load alsoconcentrates at the inner peripheral part of the transferred substrate1. The contact pressure between the master 5 and the transferredsubstrate 1 is higher on the inner peripheral side. However, in thepresent embodiment, the groove 9 a is formed in the part A. Thus, theforce concentrating at the inner peripheral part of the upper mold 9 isblocked by the groove 9 a and distributed to the outer periphery of theupper mold 9. The appropriate position and depth of the groove allow thepressure between the master 1 and the transferred substrate 1 to besubstantially uniformly distributed. The effect of the groove 10 a,formed in the lower mold 10, is similar to that of the groove 9 a in theupper mold 9 and is thus omitted.

FIG. 10 is a graph showing the distribution of pressure generatedbetween the master 5 and the transferred substrate 1 according to thefirst embodiment. In FIG. 10, a denotes the pressure distributionaccording to the present invention, whereas b denotes the pressuredistribution according to the prior art.

As shown in FIG. 10, the technique according to the present inventionresults in a pressure difference of about 1% in the entire area exceptfor the peripheral part. On the other hand, the prior art results in apressure difference of about 20% in the entire area except for theperipheral part.

FIG. 11 is a graph showing the amount of relative misalignment betweenthe master 5 and the transferred substrate according to the firstembodiment. In FIG. 11, a denotes the amount of misalignment accordingto the present invention, b denotes the amount of misalignment accordingto the prior art, and c denotes a line corresponding to a misalignmentamount of zero.

FIG. 11 indicates that a uniform pressure distribution leads to amisalignment amount of at most 1 nm. Thus, the present invention almostzeroes the misalignment amount to enable the formation of patterns of asize of about 10 nm.

Now, description will be given of the reason for and the effect ofconcentration of pressure at the center of the mold.

When planes of the mold transmit and receive pressure, their possiblecontact states are as follows. (1) The planes contact each other attheir ends so that pressure is transmitted and received at the ends ofthe planes. (2) The planes contact each other at their centers so thatpressure is transmitted and received at the centers of the planes. (3)The pressure is distributed all over the planes. (4) A small contaminantis present between the planes and the pressure concentrates at thecontaminant for transmission and reception.

However, it is very difficult to visually determine which of the fourcontact states (1) to (4) exists. Further, the contact state depends onthe structure of the press machine. Therefore, if the pressure istransmitted and received through the contact between the planes, thedistribution of pressure is unstable.

However, the instability is eliminated by the concentration of pressureat the center of the mold. In the present invention, the pressureconcentrating mechanism K causes the pressure to concentrate at thehollow portion H of the mold, that is, the inner periphery of the mold;the pressure concentrating mechanism K is composed of the free shank 6and the projection 13.

The disk-like recording media produced using the manufacturing apparatusis fixed to an air spindle motor on the basis of a positioning patterntransferred during nano imprinting. The recording media and the airspindle motor are formed into a magnetic recording apparatus through anormal process for manufacturing a HDD (Hard Disk Drive).

A magnetic head in HDD reliably scans a data signal recorded region inaccordance with servo signals recorded in a servo signal recorded regionin a recording track band in the recording media. Thus, recording andreproducing of the information are executed.

According to the present invention, a magnetic recording layer isreliably and easily formed substantially all over the surface of a2.5-inch disk substrate that is a plate-like structure; the magneticrecording layer is patterned at a pitch of at most 200 nm. This providesan ultra high-density magnetic recording system and forms servopatterns. In the present embodiment, the 2.5-inch disk substrate is usedas a plate-like structure. However, the present invention is not limitedto this.

As described above, according to the present invention, fine concave andconvex patterns of a size of at most 200 nm are precisely produced in alarge area of at least 1 square inch with a high throughput using thenano imprint technique.

In the above embodiment, the glass substrate is used as a plate-likestructure serving as a transferred substrate. However, the transferredsubstrate is not limited to this. The present method is applicable toall the plate-like members on which fine patters are to be formed. Thepresent method is also applicable to, for example, a semiconductor waferconsisting of a semiconductor material. To form an electronic circuit onthe surface of a semiconductor wafer, a method for pattern formingcalled PEP is conventionally used which method is a combination of anexposure step, a washing step, and an etching step. By applying thepresent method to a semiconductor wafer on which a resist has beenspin-coated, it is possible to form resist patterns with fine shapes onthe surface of the semiconductor wafer without the need for the exposurestep. This eliminates the need to use an expensive exposure apparatushaving a complicated configuration. Further, fine patterns can be formedwithout the need to take limits on light diffraction into account. Thisallows high-density recording media or semiconductors having a similarmicrostructure to be manufactured with a high throughput and a highyield.

Second Embodiment

In the second embodiment, description will be given of a trial exampleof phase change optical recording media such as MD.

FIGS. 12A to 12F are process diagrams of a process for manufacturingphase change optical recording media according to the second embodimentof the present invention; these figures show sectional views of aworkpiece during the respective steps.

First, a transferred substrate 21 shown in FIG. 12A is produced.Specifically, a reflection film 23 and a matrix layer 24 are depositedon a glass disk substrate 22 of a diameter of 2.5 inches; the reflectionfilm 23 consists of a platinum (Pt) film of a thickness of about 30 nmand the matrix layer 24 consists of an aluminum (Al₂O₃) film of athickness of about 50 nm. Then, a resist is applied to the matrix layer24 by the spin coat method to deposit a resist film 25.

Then, as shown in FIG. 12B, the same method as that used in the firstembodiment is used to transfer concave and convex patterns on a master26 to a surface of the resist film 25. This step is nano imprinting. Themaster 26 used is produced using a process similar to that in the firstembodiment. However, the master 25 is 65 nm in diameter and 300 μm inthickness and has a concave and convex formed region 26 a on itssurface; concentric concave and convex patterns of a width of 50 nm, aspacing of 50 nm, and a height of 100 nm are formed in the concave andconvex formed region 26 a.

Then, as shown in FIG. 12C, the transferred substrate 21 is stripped offfrom the master 26. When nano imprinting is finished, the concentricconcave and convex patterns corresponding to the concave and convexpatterns on the master 26 have been formed on the surface of the resistfilm 25 in the transferred substrate 21; the concentric concave andconvex patterns have a width of 50 nm, a spacing of 50 nm, and a heightof 100 nm.

Then, as shown in FIG. 12D, the matrix layer 24 is etched using theresist patterns as a mask. This forms a groove structure in the matrixlayer 24. The resist film 25 is removed after the etching.

Then, as shown in FIG. 12E, an indium antimony tellurium (In—Sb—Te) film27 of a thickness of about 30 nm is deposited as a phase changematerial. The film 27 covers the groove structure to form recordingtracks.

Then, as shown in FIG. 12F, an SiO₂ film 28 is deposited all over thesurface of the transferred substrate. Thus, the SiO₂ film 28 protectsthe matrix layer 24 and the indium antimony tellurium film 27. After thedeposition, the surface of the SiO₂ film 28 is flattened.

According to the present embodiment, the phase change recording mediapatterned at a pitch of 50 nm is formed substantially all over thesurface of the 2.5-inch disk substrate, a plate-like structure. Thisprovides ultra high-density phase change optical recording media. In thepresent embodiment, the 2.5-inch disk substrate is used as a plate-likestructure. However, the present invention is not limited to this.

Third Embodiment

A third embodiment is an example in which a glass disk for a hard diskdrive (HDD) is used as a plate-like structure. The third embodiment isapplied to a magnetic transfer system that produces magnetic recordingmedia with a high throughput (for example, Jpn. Pat. Appln. KOKAIPublication No. 1995-78337).

The magnetic transfer system requires a master disk having magneticsignals such as servo information recorded on its surface. It hashitherto been difficult to produce a master disk. However, the presentinvention allows the easy and inexpensive production of a magnetictransfer master disk to which the magnetic signals have beentransferred.

The magnetic transfer involves a step of tightly contacting a masterdisk with a slave disk so as to establish a precise positionalrelationship. The manufacturing apparatus according to the first orsecond embodiment reduces the amount of misalignment between the disksto at most 1 nm when pressure is applied to the disks. Further, thedisks are securely contacted with each other.

Accordingly, provided that an external bias magnetic field is appliedwith the master and slave disks pressurized between a pair of presssurfaces, magnetization information from the master disk is transferredto the slave disk and uniformly recorded all over its surface. Thisallows magnetic recording media to be manufactured with a highthroughput and a high yield.

The first to third embodiments have been described with reference to thespecific examples. However, the present invention is not limited tothese specific examples.

For example, the transferred substrate is not limited to the aboveembodiments. The structure, material, size, or the like of thetransferred substrate may be changed or selected from alternatives.

Further, in the above embodiments, the groove is formed only in theinner peripheral surface of the mold. However, the groove may be formedin both inner and outer peripheral surfaces of the mold. Further, thegroove may be formed only in the outer peripheral surface of the mold.

Fourth Embodiment

FIG. 13 is a sectional view of a manufacturing apparatus according to afourth embodiment of the present invention.

As shown in FIG. 13, in the manufacturing apparatus according to thepresent embodiment, the bottom surface of the free shank 6 and the topsurface of the projection 13 have a diameter larger than that of theworkpiece (master 5 and transferred substrate 1). Thus, if no groove ispresent in the outer peripheral surface of the upper mold 9 or lowermold 10, the pressure exerted on the upper mold 9 and lower mold 10 by apressure concentrating mechanism Ka concentrates at the outer peripheralpart of the transferred substrate 1; the pressure concentratingmechanism Ka is composed of the free shank 6 and the projection 13.

However, if the grooves 9 a and 10 a are present in the outer peripheralsurfaces of the upper mold 9 and lower mold 10 respectively, the grooves9 a and 10 a distributes the pressure concentrating at the outerperipheral part, toward the central axes of the upper mold 9 and lowermold 10.

This manufacturing apparatus is applied to the manufacturing of aplate-like structure such as small-diameter recording media, forexample, a 0.85-inch hard disk. Further, the size of the transferredsubstrate 1 varies but the present invention is applied to any size ofthe transferred substrate 1.

Fifth Embodiment

The manufacturing method according to the present invention comprises anano imprint process of pressing the master 5 against the transferredsubstrate 1 under a pressure of several tens of to several hundreds MPato transfer the concave and convex patterns on the master 5 to theresist film on the transferred substrate 1. Thus, uniform pressurizationmust be ensured. That is, it is necessary to avoid biasing the pressuredistribution to minimize the amount of relative misalignment between themaster 5 and the transferred substrate 1.

However, the surface of a glass disk, used as a material for thetransferred substrate 1, is not always very flat. Certain concaves andconvexes are present on the surface of the glass disk substrate.Further, the press surfaces of the upper mold 9 and lower mold 10 arenot always very flat as in the case of the glass disk substrate. Certainconcaves and convexes are present on the press surfaces.

Thus, in the present embodiment, the impact of the presence of concavesand convexes on nano imprinting will be considered.

FIG. 14 is a sectional view showing an essential part of the transferredsubstrate 1 pressurized between the upper mold 9 and the lower mold 10according to a fifth embodiment of the present invention.

In this case, it is assumed that the master 5, the upper mold 9, and thelower mold 10 have no concaves or convexes and that only the transferredsubstrate 1 has a local convex portion of a size of about 2 μm. That is,a convex portion T of size 2 μm is provided on the transferred substrate1.

The inventor applied a finite element method to the transferredsubstrate 1 to construct an accurate analysis model. In this analysismodel, iron (low-carbon steel) is used as a material for the molds 9 and10.

The results of the analysis will be described below.

FIG. 15A is a characteristic diagram of the distribution of pressuregenerated between the master 5 and the transferred substrate 1 accordingto the fifth embodiment. FIG. 15B is a characteristic diagram of theamount of relative misalignment between the master 5 and the transferredsubstrate 1 according to the fifth embodiment.

As shown in FIG. 15A, the distribution of the pressure between themaster 5 and the transferred substrate 1 varies within the range from−10% to +17% with reference to 10⁸ Pa (about 1,000 atm.). Further, asshown in FIG. 15B, the maximum amount of misalignment between the master5 and the transferred substrate 1 is 28 nm.

In this manner, the convex portion T on the transferred substrate 1varies the distribution of the pressure between the master 5 and thetransferred substrate 1. Marked misalignment occurs between the master 5and the transferred substrate 1. Thus, to solve this problem, theinventor has proposed a method and apparatus for manufacturing aplate-like structure as described below. Even with the transferredsubstrate 1 with the convex portion T, the method and apparatus reducesthe amount of misalignment between the master 5 and the transferredsubstrate 1 to greatly improve the precision of nano imprinting.

FIG. 16A is a perspective view of a manufacturing apparatus according tothe fifth embodiment. FIG. 16B is a partly cutaway perspective view ofthe manufacturing apparatus according to the fifth embodiment.

As shown in FIGS. 16A and 16B, the manufacturing apparatus comprises,for example, an upper die set 7, an upper plate 8, an upper mold 9having a hollow portion H formed along is central axis, two pressureequalizers 30, a lower mold 10 having a hollow portion H formed along iscentral axis, a lower plate 11, and a lower die set 12. Themanufacturing apparatus is pressurized from above by the hydraulic pressmachine.

The upper die set 7 is attached to the lower die set 12 via a pluralityof guide posts 14 so that the upper die set 7 can freely contact andleave the lower die set 12. The upper plate 8 is mounted on the bottomsurface of the upper die set 7. The upper mold 9 is supported on thebottom surface of the upper plate 8. The lower plate 11 is mounted onthe top surface of the lower die set 12. The lower mold 10 is supportedon the top surface of the lower plate 11. In this case, the previouslydescribed free shank 6 and projection 13 are omitted.

The manufacturing apparatus is mounted in the common hydraulic pressmachine shown in FIG. 6. The master 5 and the transferred substrate 1are sandwiched and pressurized between the pressure equalizers 30,described below.

FIG. 17 is an enlarged sectional view of an essential part of FIG. 16B.

As shown in FIG. 17, the pressure equalizer 30 is composed of a bufferlayer 31 and a plate member 32. That is, in the present embodiment, thefollowing are stacked in the following order from top to bottom: theupper die set 7, the upper plate 8, the upper mold 9, the buffer layer31, the plate member 32, the master 5, the transferred substrate 1, theplate member 32, the buffer layer 31, the lower mold 10, the lower plate11, and the lower die set 12. A pressure of about 325 kN (32 ton) isapplied.

A material for the buffer layer 31 is a synthetic resin (for example, aPET resin) which is about 0.5 mm in thickness and which is softer thanthe master 5 and the transferred substrate 1. A material for the platemember 32 is an iron plate (low-carbon steel) of a thickness of about1.0 mm.

The master 5 and the transferred substrate 1 are formed of the samematerials as those previously described. However, a convex portion T ofsize about 2 μm is formed in a central part of the transferred substrate1 as described in FIG. 14. Further, the size, shape, and material of themold consisting of the upper mold 9 and lower mold 10 are the same asthose previously described.

FIG. 18 is a diagram illustrating a method for applying pressure to themold according to the fifth embodiment.

As shown by arrows in the figure, pressure is applied to the vicinity ofcentral axis of the end surface of each of the die set 7 and die set 12.This allows a compressive load to concentrate at the hollow portionsformed in the upper mold 9 and lower mold 10, that is, the vicinity ofthe inner peripheral surfaces of the upper mold 9 and lower mold 10.This is a requirement for eliminating the factor causing instability inconnection with the biased abutment of the press surfaces.

The inventor used the finite element method to analyze the distributionof the pressure between the master 5 and the transferred substrate 1 andthe relative alignment between the master 5 and the transferredsubstrate 1.

The results of the analysis will be described below.

FIG. 19A is a graph showing the distribution of pressure generatedbetween the master 5 and the transferred substrate 1 according to thefifth embodiment. FIG. 19B is a graph of the amount of relativemisalignment between the master 5 and the transferred substrate 1according to the fifth embodiment.

As shown in FIG. 19A, the distribution of the pressure between themaster 5 and the transferred substrate 1 is considerably uniform. Therange of variation is −4% to +8% with reference to 10⁸ Pa (about 1,000atm.). As shown in FIG. 19B, the amount of misalignment between themaster 5 and the transferred substrate 1 decreased to 22 nm. That is,the use of the previously described manufacturing method and apparatusprovides a robust design solution for a variation in the board thicknessof the transferred substrate 1.

Now, description will be given of how the inventor obtained thepreviously described configuration.

As previously described, the applicant has proposed the room temperatureimprinting technique in Jpn. Pat. Appln. KOKAI Publication No.2003-157520. This technique is characterized in that a buffer layer isinterposed between an upper mold and a transferred substrate; the bufferlayer consists of a material softer than a master and the transferredsubstrate (PET resin) and in that pressure is applied to the transferredsubstrate via the buffer layer to transfer concave and convex patternson the master to the surface of the transferred substrate.

If the transferred substrate has a varying board thickness, that is, thetransferred substrate has convex portions, the buffer layer iselastically deformed under pressure. That is, the buffer layer acts as acushion material that relaxes the pressure to absorb the variation inthe thickness of the transferred substrate.

However, the PET resin, a material for the buffer layer, has a smallelastic coefficient and a Poisson ratio of 0.3. Consequently, the bufferlayer is likely to be expanded in a plane direction perpendicular to theaxial direction when pressure is applied to the buffer layer in itsaxial direction.

Accordingly, when convex portions are provided at a position of thetransferred substrate which contacts the buffer layer, the transferredsubstrate is moved in the plane direction together with the bufferlayer. Thus, relative misalignment occurs between the master and thetransferred substrate. Actually, the amount of relative misalignmentbetween the master and the transferred substrate is of the order of μm.

Thus, the following conclusion was drawn. Provided that a structurewhich is soft in the axial direction (the direction in which pressure isapplied) and which is rigid in the plane direction (the directionorthogonal to the axial direction) is interposed between the upper moldand the transferred substrate in place of the buffer layer, the convexportions of the transferred substrate are absorbed to suppress therelative misalignment between the master and the transferred substrate.As a result, all the conditions are met.

Thus, in the present embodiment, the pressure equalizers 30 areinterposed between the mold that is the upper mold 9 or the lower mold10 and the workpiece that is the master 5 and transferred substrate 1.The inventors executed analysis to find that all the conditions weremet. In this case, as shown in FIGS. 20A to 20B, the master 5 isdisposed under the transferred substrate 1.

FIG. 20A is a sectional view of the pressure equalizer 30 with nopressure applied the master 5 or the transferred substrate 1 accordingto the fifth embodiment. FIG. 20B is a sectional view of the pressureequalizer 30 with pressure applied to the master 5 and the transferredsubstrate 1 according to the fifth embodiment.

As shown in FIG. 20A, the master 5 and transferred substrate 1 to bepressurized are placed between the upper mold 9 and the lower mold 10.The transferred substrate 1 comprises the concave portion T, while themaster 5 comprises no concave portion. The pressure equalizer 30 isinterposed between the upper mold 9 and the transferred substrate 1. Thepressure equalizer 30 is composed of a buffer layer 31 placed adjacentto the upper mold 9 and made of resin and a plate member 32 placedadjacent to the transferred substrate 1 and made of a metal. The bufferlayer 31 and the plate member 32 are laid on top of each other. Theplate material 32 and the buffer layer 31 are not joined together. Thepressure equalizer 30 is also interposed between the lower mold 10 andthe master 5. The pressure equalizer 30 is composed of a buffer layer 31placed adjacent to the lower mold 10 and a plate member 32 placedadjacent to the master 5.

Description will be given only of the transferred substrate 1 having theconvex portion T.

A compressive load imposed on the upper mold 9 is transmitted to thebuffer layer 31, which is thus elastically deformed. That is, the bufferlayer 31, which has a small elastic coefficient, is contracted in theaxial direction and expanded in the plane direction as shown by thealternate long and two short dashes line in FIG. 20B. The buffer layer31 thus absorbs the convex portion T of the transferred substrate 1 viathe plate member 32. The compressive load transmitted to the bufferlayer 31 acts on the plate member 32.

When the buffer layer 31 is expanded in the plane direction, the platemember 32 receives a force that shifts the plate member 32 from thebuffer layer 31 in the plane direction. However, the iron plate(low-carbon steel) constituting the plate member 32 is made of a hardmaterial. The iron plate has a much larger modulus of longitudinalelasticity than the PET resin constituting the buffer layer 31 (about100 times). Consequently, when the buffer layer 31 is deformed,expanding in the plane direction, slippage occurs on the interface. Thisprevents the plate member 32 from moving in the plane direction even.

On the other hand, the plate member 32 is formed to be thin enough to bedeformed to follow the shape of the transferred substrate 1 whensubjected to a compressive load from the buffer layer 31; the platemember 32 comes into direct contact with the transferred substrate 1.The plate member 32 thus uniformly transmits the compressive load to thetransferred substrate 1. Even if the concave portion T is present allover the surface of the transferred substrate, the plate member 32uniformly transmits the compressive load to the transferred substrate 1.The deformation of the plate member 32 is not “contraction under avertical load” but “out-of-plane deformation of a leaf spring”.Therefore, the plate member 32 is not significantly expanded in theplane direction.

As described above, the plate member 32, which contacts the master 5 andtransferred substrate 1, is not moved in the plane direction even whenpressurized by the upper mold 9 and lower mold 10. As a result, thetransferred substrate 1 is not moved together with the plate member 32in the plane direction. Therefore, relative misalignment does not occurbetween the master 5 and the transferred substrate 1. This meets all therequirements for the nano imprint process.

Exactly the same effects are produced even if the transferred substrate1 has a concave portion or even if the transferred substrate 1 has aplurality of concave and convex portions. Not only if the transferredsubstrate 1 has a concave and a convex but also if the master 5 has aconcave and a convex portion, exactly the same effects are producedprovided that the pressure equalizer 30 is interposed between the master5 and the lower mold 10. Further, the thickness of the plate member 32is appropriately set in accordance with specifications such as thematerial constituting the plate member and the flatness of thetransferred substrate 1.

Now, description will be given of a manufacturing apparatus according toa variation of the fifth embodiment.

In the present variation, the previously described grooves 9 a and 10 a(see FIG. 7) are formed in the inner peripheral surfaces of the uppermold 9 and lower mold 10, respectively, according to the fifthembodiment. That is, the manufacturing apparatus according to thepresent variation comprises a technique for providing the pressureequalizer 30 between the upper mold 9 and the master 5 or between thelower mold 10 and transferred substrate 1 and a technique for formingthe grooves 9 a and 10 a in the inner peripheral surfaces of the uppermold 9 and lower mold 10 respectively.

As described in the first embodiment, when the grooves 9 a and 10 a areformed in the peripheral surfaces of hollow portions H of the upper mold9 and lower mold 10 respectively, a difference in pressure between themaster 5 and the flat transferred substrate 1 is at most 1%. The grooves9 a and 10 a are thus effective.

Thus, the inventor used the manufacturing apparatus having the grooves 9a and 10 a and the pressure equalizer 30 to make experiments ontransfers to the transferred substrate 1 having a convex portion T of asize of about 2 μm.

FIG. 21A is a graph showing the distribution of pressure generatedbetween the master 5 and the transferred substrate 1 according to thevariation of the fifth embodiment. FIG. 21B is a graph of the amount ofrelative misalignment between the master 5 and the transferred substrate1 according to the variation of the fifth embodiment.

FIG. 21A shows that the pressure distribution is more uniform. Thisdemonstrates that the means for providing the pressure equalizer 30 isconsistent with the means for providing the grooves 9 a and 10 a in theupper mold 9 and lower mold 10 respectively.

Sixth Embodiment

FIG. 22 is a partly cutaway perspective view showing a manufacturingapparatus according to a sixth embodiment of the present invention.

As shown in FIG. 22, the manufacturing apparatus comprises the freeshank 6, the upper die set 7, the upper plate 8, the upper mold 9, thelower mold 10, the lower plate 11, the lower die set 12, and theprojection 13 arranged in this order from top to bottom. Themanufacturing apparatus is pressurized from above by the hydraulic pressmachine.

The upper die set 7 is attached to the lower die set 12 via a pluralityof guide posts 14 so that the upper die set 7 can freely contact andleave the lower die set 12. The upper plate 8 is mounted on the bottomsurface of the upper die set 7. The upper mold 9 is supported on thebottom surface of the upper plate 8. The lower plate 11 is mounted onthe top surface of the lower die set 12. The lower mold 10 is supportedon the top surface of the lower plate 11.

The pair of press surfaces according to the present invention iscomposed of the bottom surface of the upper mold 9 and the top surfaceof the lower mold 10. The master 5 and the transferred substrate 1 aresandwiched and pressurized between the bottom surface of the upper mold9 and the top surface of the lower mold 10. The pressure equalizer 30 isinterposed only between the upper mold 9 and the master 5; the pressureequalizer 30 consists of the buffer layer 31 and the plate member 32.

Even if the pressure equalizer 30 is thus interposed only between theupper mold 9 and the master 5, it absorbs the concave and convex formedon the master 5 or transferred substrate 1. That is, pressure is applieduniformly all over the surfaces of the master 5 and transferredsubstrate 1.

The present invention is not limited to the previously describedembodiments proper. In implementation, the present invention can beembodied by varying the components of the embodiments without departingfrom the spirit of the present invention. Various inventions can beformed by appropriately combining a plurality of the componentsdisclosed in the previously described embodiments.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A method for manufacturing a plate-like structure, the methodcomprising a step of transferring concave and convex patterns on amaster to a surface of a transferred substrate by sandwiching the masterprovided with the concave and convex patterns and the transferredsubstrate, between a press surface of a hollow cylindrical upper moldand a press surface of a hollow cylindrical lower mold, and pressurizingcentral parts of the upper and lower molds to apply pressure to themaster and the transferred substrate, wherein a compressive load imposedon inner peripheral portions of the upper and lower molds is blocked anddistributed toward outer peripheries of the upper and lower molds.
 2. Amethod for manufacturing a plate-like structure, the method comprising astep of transferring concave and convex patterns on a master to asurface of a transferred substrate by sandwiching the master providedwith the concave and convex patterns and the transferred substrate,between a press surface of an upper mold and a press surface of a lowermold, and applying pressure to the master and the transferred substrate,wherein a compressive load imposed on outer peripheral portions of theupper and lower molds is distributed toward central axes of the upperand lower molds.
 3. The method for manufacturing a plate-like structureaccording to claim 1, wherein at least one of the press surfaces of theupper and lower molds is expanded or contracted in a direction parallelto the press surface by the pressure applied by the upper and lowermolds, to absorb deformation of the master and transferred substrate,and the press surface is further deformed to follow the shape of themaster or the transferred substrate to apply the pressure uniformly tothe master and transferred substrate.
 4. The method for manufacturing aplate-like structure according to claim 2, wherein at least one of thepress surfaces of the upper and lower molds is expanded or contracted ina direction parallel to the press surface by the pressure applied by theupper and lower molds, to absorb deformation of the master andtransferred substrate, and the press surface is further deformed tofollow the shape of the master or the transferred substrate to apply thepressure uniformly to the master and transferred substrate.
 5. Themethod for manufacturing a plate-like structure according to claim 1,wherein the transferred substrate has a transferred layer made of aresist material, on its surface, and the concave and convex patterns aretransferred at a temperature lower than a glass transition temperatureof the transferred layer under a pressure of 1 atm.
 6. The method formanufacturing a plate-like structure according to claim 2, wherein thetransferred substrate has a transferred layer made of a resist material,on its surface, and the concave and convex patterns are transferred at atemperature lower than a glass transition temperature of the transferredlayer under a pressure of 1 atm.
 7. The method for manufacturing aplate-like structure according to claim 1, wherein the master and thetransferred substrate contain any one of metal, alloy, metal oxide, aninorganic material, a ceramic material, a semiconductor, and glass. 8.The method for manufacturing a plate-like structure according to claim2, wherein the master and the transferred substrate contain any one ofmetal, alloy, metal oxide, an inorganic material, a ceramic material, asemiconductor, and glass.
 9. The method for manufacturing a plate-likestructure according to claim 1, wherein at least one of the presssurfaces of the upper and lower molds comprises: a buffer layer which isexpanded or contracted in a direction parallel to the press surface bythe pressure applied by the upper and lower molds, to absorb deformationof the master and transferred substrate; and a plate member provided ona surface of the buffer layer which is adjacent to the master or thetransferred substrate, the plate member being deformed by the pressurereceived via the buffer layer, so as to follow the shape of the masteror transferred substrate.
 10. The method for manufacturing a plate-likestructure according to claim 2, wherein at least one of the presssurfaces of the upper and lower molds comprises: a buffer layer which isexpanded or contracted in a direction parallel to the press surface bythe pressure applied by the upper and lower molds, to absorb deformationof the master and transferred substrate; and a plate member provided ona surface of the buffer layer which is adjacent to the master or thetransferred substrate, the plate member being deformed by the pressurereceived via the buffer layer, so as to follow the shape of the masteror transferred substrate.
 11. The method for manufacturing a plate-likestructure according to claim 9, wherein a material for the buffer layeris any one of plastics, rubber, and a polyethylene terephthalate resin.12. The method for manufacturing a plate-like structure according toclaim 10, wherein a material for the buffer layer is any one ofplastics, rubber, and a polyethylene terephthalate resin.
 13. The methodfor manufacturing a plate-like structure according to claim 1, whereinthe transferred substrate is mounted in a hard disk drive, and theconcave and convex patterns are transferred to the surface of thetransferred substrate in order to form servo patterns on the substrate.14. The method for manufacturing a plate-like structure according toclaim 1, wherein the transferred substrate is a semiconductor wafer, andthe concave and convex patterns are transferred to the surface of thesemiconductor wafer.
 15. An apparatus which manufactures a plate-likestructure, the apparatus transferring concave and convex patterns on amaster to a surface of a transferred substrate by sandwiching the masterprovided with the concave and convex patterns and the transferredsubstrate, between a press surface of a hollow cylindrical upper moldand a press surface of a hollow cylindrical lower mold, and applyingpressure to the master and the transferred substrate, wherein theapparatus comprises grooves formed in inner peripheral surfaces of theupper and lower molds to block a compressive load concentrating at innerperipheral portions of the upper and lower molds to distribute thecompressive load toward outer peripheries of the upper and lower molds.16. An apparatus which manufactures a plate-like structure, theapparatus transferring concave and convex patterns on a master to asurface of a transferred substrate by sandwiching the master providedwith the concave and convex patterns and the transferred substrate,between a press surface of an upper mold and a press surface of a lowermold, and applying pressure to the master and the transferred substrate,wherein the apparatus comprises grooves formed in outer peripheralsurfaces of the upper and lower molds to distribute a compressive loadconcentrating at outer peripheral portions of the upper and lower moldstoward central axes of the upper and lower molds.